1. Field of the Invention
The present disclosure relates to an imaging apparatus.
2. Description of the Related Art
A digital camera, one type of present-day imaging apparatus, is mounted with a liquid crystal display monitor on a rear side of a main body. Immediately after an image is shot, the image can be seen on the liquid crystal display monitor, which is very convenient for a photographer. There are many types of digital cameras that can shoot not only still images, but also moving images, which attests to enhanced performance of digital cameras. Some digital cameras are of a lens-interchangeable type, in general referred to as a digital single-lens reflex type, and digital cameras of this type are increasing. By selecting a lens suitable for a shooting purpose, the shot image quality has been enhanced.
In the above-described situation, however, lens operations during moving-image shooting—e.g., a zooming operation, an AF operation (autofocusing operation), an iris operation (diaphragm adjusting operation), and an optical camera shake correction operation—cause a vibration and noise. Since the sound of the vibration and noise is recorded at a high level, the video image played back is likely to be barely appreciable. An effect of lens operation noise reduction processing is very important for a digital camera with a moving-image shooting feature.
Lens operation noise reduction processing is disclosed in Unexamined Japanese Patent Publication No. 2002-344787. In the method of this conventional art, as lens operation noise reduction processing, a microphone for detecting a vibration caused by a lens operation is provided in addition to a microphone for recording sound so that the antiphase of a signal detected by the former microphone is cancelled from an output signal of the latter microphone. In another method of Unexamined Japanese Patent Publication No. 2002-344787, lens operation noise reduction processing is performed using the aforementioned cancellation technique only during a zooming operation of the lens so as to mitigate an adverse effect, such as distortion of recorded data during normal time.
Unexamined Japanese Patent Publication No. 2007-311850 discloses a directivity synthesis method using output signals of a plurality of non-directivity microphones. In this method, output signals are synthesized with sound signals generated by delaying the output signals so that the synthesized sound signals have left and right stereo directivity (high stereo separation level).
Unexamined Japanese Patent Publication No. 2007-311850 discloses another method for reducing a noise effect. In this method, when a noise effect is significant at a low sound input level, the synthesis ratio is controlled to reduce the stereo separation level in order to reduce the noise effect.
Unexamined Japanese Patent Publication No. 2010-226142 discloses a method for integrating, in an interchangeable-type lens, data on a lens-specific noise processing algorithm.
However, the conventional imaging apparatus has the following problems:
A typical imaging apparatus continuously performs an AF operation during moving-image shooting, but the operating distance and speed of a focus lens change depending on the lens f-number. At a small lens f-number, the focal depth is small. In order to focus, the operating distance of a focus lens is small, and the operating speed is not high. Conversely, at a large lens f-number, the focal depth is large. In order to focus, the operating distance of a focus lens is large, and the operating speed is high. As a result, noise caused by a lens AF operation is greater at a large lens f-number than at a small lens f-number.
For lens operation noise reduction processing, there exist conventional imaging apparatuses having a noise processing algorithm compatible with different lens types, including an interchangeable type. However, changes in the AF operation noise level depending on the lens f-number have not been addressed. Noise reduction processing specific to the lens f-number has not been achieved.
A noise frequency peak is often lens-unique at different f-numbers while the lens performs an AF operation. Noise reduction processing by, e.g., a notch filter, is uniform processing that does not enable sound processing specific to different f-numbers. For instance, when sound processing is performed assuming that noise is generated at a small lens f-number and a video image is shot at a large lens f-number, the video image played back is barely appreciable due to a high noise level. Conversely, when sound processing is performed assuming that noise is generated at a large lens f-number and a video image is shot at a small lens f-number, the sound quality of the video image played back is deteriorated due to sound over-suppression.
According to the present disclosure, there is provided an imaging apparatus that can record a clear video image at a low noise level even when the lens f-number is variable.
An imaging apparatus of the present disclosure includes a lens, a microphone for recording sound, and a filter configured to reduce noise contained in an output signal of the microphone. The noise reduction level of the filter is controlled according to the lens f-number so that the noise reduction level of the filter is increased when the lens f-number is large than when the lens f-number is small.
According to the present disclosure, there is provided an imaging apparatus that can record a clear video image at a low noise level by performing sound processing specific to AF lens noise generated by an AF operation that changes depending on the lens f-number.